Majorana vs. Dirac sterile neutrinos lighter than M<inf>W</inf> at the LHC

We propose to study the leptonic decays W± → e±e±μ∓ν and W± → μ±μ±e∓ν at
the LHC to discover sterile neutrinos with masses below MW , and discriminate their Majorana
or Dirac character. These decays are induced by a sterile neutrino N that goes on mass shell in
the intermediate state. We find that, even though the final (anti-)neutrino goes undetected and
thus lepton number is unchecked, one can distinguish between the Majorana vs. Dirac character
of the intermediate sterile neutrino by comparing the production of e±e±μ∓ vs. μ±μ±e∓,
provided the N-e and N-μ mixings are different enough. Alternatively, one can also distinguish
the Majorana vs. Dirac character by studying the energy spectra of the opposite charge lepton,
a method that works even if the N-e and N-μ mixings are equal.